Non-aqueous lithium ion electrochemical cells typically include an anode, a lithium electrolyte prepared from a lithium salt dissolved in one or more organic solvents and a cathode of an electrochemically active material, typically an insertion compound. During discharge, lithium ions from the anode pass through the liquid electrolyte to the electrochemically active material of the cathode where the ions are taken up with the simultaneous release of electrical energy. During charging, the flow of ions is reversed so that lithium ions pass from the electrochemically active cathode material through the electrolyte and are plated back onto the lithium anode.
Recently, the lithium metal anode has been replaced with a carbon anode such as coke or graphite intercalated with lithium ions to form Li.sub.x C. In operation of the cell, lithium ion passes from the carbon through the electrolyte to the cathode where it is taken up just as in a cell with a metallic lithium anode. During recharge, the lithium ion is transferred back to the anode where it reintercalates into the carbon. Because no metallic lithium is present in the cell, melting of the anode does not occur even under abuse conditions. Also, because lithium is reincorporated into the anode by intercalation rather than by plating, dendritic and spongy lithium growth does not occur.
Composite electrodes refer to cathodes and anodes wherein the cathode is comprised of materials other than compatible cathodic materials and the anode is comprised of materials other than compatible anodic materials. Typically, the composite electrode contains a polymer which acts to bind the composite materials together. Composite electrodes are well known in the art. For example, a composite cathode can comprise a compatible cathodic material, a conductive material, and a polymeric binder. Similarly, for example, a composite anode can comprise a compatible intercalation anodic material and a polymeric binder.
In order to enhance the overall current produced by solid or liquid batteries, it is conventional to employ several electrochemical cells in a battery. When so employed, the current from each of the cells is accumulated so that the total current generated by the battery is roughly the sum of the current generated from each of the individual electrochemical cells employed in the battery. One method for accumulating the current from individual electrochemical cells employs a current collector that is attached to the cathode or the anode of the electrochemical cell. Typically, the current collector is a metal foil or grid or a conductive plastic which is coupled to other current collectors in the battery so that the current generated by each cell is collected and accumulated over all of the cells. Current collectors are described, for example, in U.S. Pat. Nos. 4,925,752, 5,011,501, 5,441,830 and 5,464,707. Thus, the total current generated by the battery is a summation of the current generated by each of the electrochemical cells employed in the battery minus whatever current is lost due to resistance in the current collector. To minimize resistance, a large contact surface area between the current collector and the electrode is employed. Notwithstanding the benefits of using current collectors in electrochemical cells, metal current collectors often do not adhere to electrodes. This inevitably reduces the performance of the cell and battery.